There are a number of applications for uniform magnetic fields that require precise characteristics, usually at relatively high frequencies. Many of these applications use circuitry developed for producing accurately regulated alternating current waves from a source of direct current. More recently, electromagnetic recording systems have received attention to the generation of more precise magnetic fields than heretofore. The most important application currently is for magnetic bubble data storage apparatus. In this application a pair of magnetic field generating devices are arranged to create a rotating magnetic field of precise characteristics in the place of a magnetic bubble storage chip. A sine wave current is made to traverse each inductor for generating a component of the rotating field, and that current is controlled in amplitude and phase to the degree required for the application at hand. The requirement is frequently strict, and while many circuit arrangements have been put together for operating magnetic bubble storage devices, there remain too many shortcomings in the art.